Go To: 192.168.1.1 ..... type this in your browser
Sign in to your Router...Make sure they cannot sign in to your Router...change Password...Then
Go To : Parental Control...take it from there.
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PS: Here is a good Ref for you Re Passwords.
https://www.grc.com/haystack.htm
Tom
QIP 7100 1,YAMAHA ATS 1080,QIP 7216 P2, iPad 2 WiFi,iPhone SE